The present invention disclosed herein relates to an apparatus and method for measuring IQ imbalance, and more particularly, to an apparatus and method for measuring IQ imbalance for an optical receiver.
As a receiver in a high speed transmission system using an optical signal, a coherent optical receiver is being researched. The coherent optical receiver outputs an in-phase (I) signal and a quadri-phase (Q) signal. In a non-ideal optical receiver, amplitude imbalance and phase imbalance may occur between the output I-signal and Q-signal. Since these IQ imbalances distort an original signal, a signal receiving performance of the optical receiver may be lowered.
The lowered performance of the optical receiver may be prevented by measuring IQ imbalances thereof and compensating for a signal on the basis of the measured IQ imbalances in an optical transmitter and the optical receiver. In order to measure the IQ imbalances digitally, a plurality of signal samples may be used. However, in order to estimate the IQ imbalances digitally, a lot of signal samples may be required and accordingly a lot of calculations may be required for a high speed signal.